Evaporation circuit for alternative refrigerant in a refrigeration system

ABSTRACT

An evaporator circuit for a second refrigerant used in conjunction with a refrigeration circuit of the type operating a refrigeration cycle. The evaporator circuit has a heat exchange stage having a heat exchanger in a refrigerant accumulator in which the second refrigerant is in heat-exchange relation with the first refrigerant circulating in the heat exchanger in the evaporation stage of the refrigeration circuit. The heat exchanger is positioned in the refrigerant accumulator so as to be immersed in the second refrigerant such that the second refrigerant releases heat to the first refrigerant circulating in the heat exchanger. An evaporator stage has an evaporator in which the second refrigerant absorbs heat from a fluid passing through the evaporator, so as to cool the fluid, whereby the second refrigerant circulates between the heat exchange stage and the evaporator stage.

TECHNICAL FIELD

The present invention generally relates to refrigeration systems and, more particularly, to refrigeration systems having circuits used in conjunction with a main refrigeration circuit.

BACKGROUND ART

With the constant evolution of technology, the demand for electricity has greatly increased in industrialized countries over the last decades. A major portion of households and offices of industrialized countries are now equipped with electrical appliances that did not exist a few decades ago. Computers, air-conditioning units, microwave ovens and home entertainment systems are a few of these appliances that are widely used in the industrialized countries.

In these industrialized countries, a major portion of the industries have adopted a Monday-to-Friday daytime work schedule. As a consequence, a generally corresponding part of the population has similar hours of activity and this has created peak-hour periods for energy demand. Accordingly, electricity consumption is higher during these hours of activity. In typical supply-and-demand logic following this peaked daytime demand, power companies have adopted two-way electricity tariffs, with cheaper rates at night.

It is however of concern to reduce the quantity of some types of refrigerants, which are considered to some level harmful for the environment. For instance, some types of fluorine-based refrigerants are subjected to environmental concerns. This factor must therefore be considered when designing refrigeration systems which are energy efficient, but that increase the volume of conduits of refrigerant.

SUMMARY OF INVENTION

Therefore, it is a feature of the present invention to provide a novel refrigeration system.

It is a further feature of the present invention to provide a refrigeration system having an evaporation circuit that relates evaporators of the refrigeration cabinets to a main refrigeration cycle.

It is a still further feature of the present invention to provide a refrigeration system with energy storage.

It is a still further feature of the present invention to provide a method for storing energy.

Therefore, in accordance with the present invention, there is provided an evaporator circuit for a second refrigerant used in conjunction with a refrigeration circuit of the type operating a refrigeration cycle having a compression stage, a condensation stage, an expansion stage, and an evaporation stage with a first refrigerant, comprising a heat exchange stage having at least one heat exchanger in a refrigerant accumulator in which the second refrigerant is in heat-exchange relation with the first refrigerant circulating in the heat exchanger in the evaporation stage of the refrigeration circuit, the heat exchanger being positioned in the refrigerant accumulator so as to be immersed in the second refrigerant such that the second refrigerant releases heat to the first refrigerant circulating in the heat exchanger, and an evaporator stage having at least one evaporator in which the second refrigerant absorbs heat from a fluid passing through the evaporator, so as to cool the fluid, whereby the second refrigerant circulates between the heat exchange stage and the evaporator stage.

Further in accordance with the present invention, there is provided a refrigeration system of the type having a refrigeration circuit having a compression stage, a condensation stage, an expansion stage and an evaporation stage through which a first refrigerant circulates, further comprising an evaporator circuit through which circulates a second refrigerant between a heat exchange stage having at least one heat exchanger in a refrigerant accumulator in which the second refrigerant is in heat-exchange relation with the first refrigerant circulating in the heat exchanger in the evaporation stage of the refrigeration circuit, the heat exchanger being positioned in the refrigerant accumulator so as to be immersed in the second refrigerant such that the second refrigerant releases heat to the first refrigerant circulating in the heat exchanger, and an evaporator stage having at least one evaporator in which the second refrigerant absorbs heat from a fluid passing through the evaporator, so as to cool the fluid for refrigeration, whereby the second refrigerant circulates between the heat exchange stage and the evaporator stage.

Still further in accordance with the present invention, there is provided a refrigeration system of the type having a refrigeration circuit having a compression stage, a condensation stage, an expansion stage and an evaporation stage through which a first refrigerant circulates, comprising at least one compressor at the compression stage, the compressor being a magnetic-bearing compressor, and pressure increasing means upstream of the expansion stage, so as to increase the pressure of the first refrigerant for subsequently being fed to the expansion stage.

BRIEF DESCRIPTION OF DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of a refrigeration system in accordance with a first embodiment of the present invention, in which an evaporation circuit is pressurized for refrigerant circulation;

FIG. 2 is a schematic view of a refrigeration system in accordance with a second embodiment of the present invention, in which an evaporation circuit operates with pumps for refrigerant circulation;

FIG. 3 is a schematic view of a refrigeration system in accordance with a third embodiment of the present invention, without any auxiliary energy accumulator;

FIG. 4 is a perspective view of a transfer accumulator with plate heat-exchangers in accordance with the embodiments of the present invention, having a wall thereof removed to show an interior thereof; and

FIG. 5 is a perspective view of coil heat-exchanger to be used with the transfer accumulator of the present invention, as an alternative to a plate heat exchanger.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, and more particularly to FIG. 1, a refrigeration system in accordance with a first embodiment of the present invention is generally shown at 10. The refrigeration system 10 has a main circuit 11 in which a first refrigerant circulates from stage to stage of a refrigeration cycle.

More specifically, the main circuit 11 has a compression stage 12, in which the first refrigerant will be compressed. The main circuit 11 has a condensing stage 14 and, optionally, a heat-reclaim stage 15, in which heat will be released from the compressed first refrigerant. Thereafter, the main circuit 11 has an expansion stage 16, in which the first refrigerant in the main circuit 11 will be expanded in view of the subsequent evaporation. The main circuit 11 has an evaporation stage 18, in which the first refrigerant will absorb heat. The first refrigerant then returns to the compression stage 12 to complete the refrigeration cycle.

In addition to the main circuit 11, the refrigeration system 10 has an evaporator circuit 19 and a defrost circuit 54. The main circuit 11 and the evaporator circuit 19 interact at the evaporation stage 18, as will be described hereinafter. As the main circuit 11 and the evaporator circuit 19 are closed with respect to one another, the refrigerant (hereinafter—the second refrigerant) in the evaporator circuit 19 is physically separated from the first refrigerant in the main circuit 11. The first refrigerant of the main circuit 11 is typically a fluorine-based refrigerant, as it will go through a complete refrigeration cycle (and be exposed to outdoor temperature variations), whereas the refrigerant in the evaporator circuit 19 is preferably an alcohol-based refrigerant, such as a mixture of glycol and water, as it will be subjected to less temperature variation in its use.

Main Circuit 11

The compression stage 12 has compressors, such as the compressors 20 in FIG. 1. The compressors 20 compress the first refrigerant of the main circuit 11. The first refrigerant is conveyed from the compression stage 12 to the condensing stage 14 and/or the heat-reclaim stage 15. More specifically, lines 22 interconnect the compressors 20 to the condensing stage 14. Line 24 diverges from the lines 22 so as to reach the heat-reclaim stage 15. It is pointed out that valves and/or controllers are provided in the lines 22 and/or 24 in order to control the quantity of the first refrigerant reaching the condensing stage 14 versus the heat-reclaim stage 15. Moreover, systems such as an oil recuperator are used in conjunction with the lines 22 and/or 24 to ensure optimal operating parameters of the first refrigerant.

The condensing stage 14 has a condenser 40, at which heat will be released from the first refrigerant. As is well known in the art, the first refrigerant is typically compressed as a function of the fluid that is in heat-exchange relation with the condenser 40 (e.g., air blown across the condenser 40), so as to release heat therefrom.

The heat-reclaim stage 15 has a heat exchanger 50 in which the first refrigerant is in heat-exchange relation with a second refrigerant circulating in the defrost circuit 54, or, alternatively, a medium that will absorb heat from the first refrigerant (e.g., air from a ventilation duct, water heater, or the like). Lines 52 connect downstream ends of the condenser 40 and heat exchanger 50 to a reservoir 62 (i.e., a receiver). The lines 52 will convey the first refrigerant to transfer accumulators 80 and 80′ of the evaporation stage 18, and have expansion valves 60 thereon of the expansion stage 16.

The transfer accumulators 80 and 80′ will be described in further detail hereinafter. The transfer accumulators 80 and 80′ represent the evaporation stage 18 of the main circuit 11, as the first refrigerant circulating in lines 52 will absorb heat therein. Thereafter, lines 82 relate the transfer accumulators 80 and 80′ to the compressors 20, whereby the main circuit 11 is closed and the refrigeration is completed.

Evaporator Circuit 19

The transfer accumulators 80 and 80′ are heat-exchanger reservoirs (i.e., refrigerant accumulators) that will receive the second refrigerant. The first refrigerant will circulate through a reservoir portion of the transfer accumulators 80 and 80′ by way of heat exchangers (such as coils). Accordingly, the first refrigerant will absorb heat from the second refrigerant by circulating through the transfer accumulators 80 and 80′, whereby evaporation of the first refrigerant will occur in this heat-exchange stage.

The reservoir portion of the transfer accumulators 80 and 80′ is part of the evaporator circuit 19 in which the second refrigerant circulates. More specifically, the transfer accumulators 80 and 80′ are each connected to a feed line 84 that will supply evaporators 86 (only one of which is shown in FIG. 1) with the second refrigerant. The feed line 84 has a feed header 92.

The refrigeration system 10 is typically used to cool refrigerators, foodstuff refrigerated cabinets, freezers and the like. One of the evaporators present in these enclosures is illustrated at 86 in FIG. 1. For clarity of the figures, only one of the evaporators 86 is illustrated, but the refrigeration system 10 typically has a plurality of evaporators 86. Lines 88, incorporating return header 93, collect the second refrigerant out of the evaporators 86, and return the second refrigerant to the transfer accumulators 80 and 80′, whereby the cycle of the second refrigerant in the evaporator circuit 19 is completed, following this evaporator stage.

In the first embodiment of the present invention, a pressure source 90 in conjunction with a control system (e.g., solenoid valves and a controller) are provided so as to control the feed of the second refrigerant to the evaporators 86. The pressure of the pressure source 90 will cause a displacement of the second refrigerant in the evaporator circuit 19. More specifically, the pressure source 90 is connected to pressure lines 91, which are connected to the transfer accumulators 80 and 80′, as well as the feed header 92 and the return header 93 of the evaporator circuit 19. Moreover, the pressure lines 91 are also connected to the energy accumulator 94, as will be described hereinafter. Valves A1, A2, B1, B2, C1, C2, D1, D2, E1, E2 and F1 are provided in the pressure lines 91 or evaporator circuit 19 and are associated with a controller that controls the feed of refrigerant in the evaporator circuit 19.

Operating Sequence

Referring to FIG. 1, the operating sequence of the refrigeration system 10 for the feed of the second refrigerant to the evaporators 86 is now described.

A first one of the transfer accumulators, e.g., transfer accumulator 80, will be used to supply the evaporators 86 with the second refrigerant, whereas the other transfer accumulator 80 will be in heat-exchange relation with the first refrigerant passing therethrough to release heat to the first refrigerant, and hence be cooled down for a subsequent feed to the evaporator 86. In this case, valve A2 on the pressure line 91, valve B2 on the feed line 84, and valve C1 on the line 88, will all be open, while valves A1 on the pressure line 91, B1 on the feed line 84, and C2 on the line 88 are all closed.

Therefore, the pressure from the pressure source 90 will increase the pressure in the transfer accumulator 80, whereby the second refrigerant accumulated in a cool state therein (as it has released heat to the first refrigerant beforehand), exits the transfer accumulator 80 through the feed line 84.

The second refrigerant is conveyed in the feed line 84, through the feed header 92, to reach the evaporators 86, in which the second refrigerant will absorb heat to cool the refrigerated cabinets.

Thereafter, the second refrigerant in a heated state, having gone through the evaporators 86, will be conveyed in lines 88, through the return header 93, as a result of the pressure from the pressure source 90 and the network of valves. The second refrigerant reaches the transfer accumulator 80′ through the line 88. Therefore, the transfer accumulator 80′ will accumulate the second refrigerant in the heated state, having absorbed heat in the evaporators 86 to cool the refrigerated cabinets. The second refrigerant in its heated state gathers in the transfer accumulator 80′, and is in heat exchange with the first refrigerant such that the second refrigerant is cooled down to a cool state. Therefore, the second refrigerant in the transfer accumulator 80′ reaches suitable conditions so as to be sent subsequently to the evaporators 86 to absorb heat.

The transfer accumulators 80 and 80′ are provided with level detectors (not shown) that are interconnected to the controller. When the transfer accumulator 80 reaches a low level of the second refrigerant, the valves are actuated so as to switch the duty of supplying the evaporators 86 with the second refrigerant in its cool state to the transfer accumulator 80′, while the transfer accumulator 80 collects the second refrigerant from the evaporators 86. More specifically, for this second sequence, the valves A2, B2 and C1 are closed, while the valves A1, B1 and C2 are opened.

The refrigeration system 10 described above has the advantage of reducing the amount of fluorine-based refrigerant when compared to refrigeration systems of similar capacity, but without evaporation circuits. Refrigeration systems typically have nonnegligible lengths of piping that will interrelate the evaporators of the evaporation state to the remainder of the refrigeration cycle. This is due to the fact that refrigerated cabinets are often spread out on the surface of a store. With the refrigeration system 10 of the present invention, the transfer accumulators 80 and 80′ are, for instance, adjacent to the pack of compressors and headers, whereby the main line of the first refrigerant extends from the condensing stage 14 to the mechanical room that contains the pack.

As the second refrigerant in the evaporator circuit 19 is generally subjected to constant conditions of heat exchange in and the transfer accumulators 80 and 80′, as well as in the evaporators 86, the second refrigerant does not undergo pressure-change phases such as compression and expansion, whereby alcohol-based refrigerant, such as glycol mixed with water, can be used. It is noted that the second refrigerant is preferably environmentally sound.

Defrost Circuit 54

Referring to FIG. 1, the heat-reclaim stage 15 has a heat exchanger 50 by which the first refrigerant is condensed in heat reclaim. In accordance with the first embodiment of the present invention, the refrigeration system 10 uses the heat-reclaim stage 15 so as to provide refrigerant for the defrost of the evaporators 86. Accordingly, the heat-reclaim stage 15 has a defrost circuit 54. The defrost circuit 54 has a defrost accumulator 55 and, optionally, heat-reclaim coils 56. The defrost circuit 54 has lines 57 by which the various components of the defrost circuit 54, namely the defrost accumulator 55 and the heat reclaim coils 56, a feed header 58 and a return header 59, are connected to the heat exchanger 50. Pumps and other devices, such as valves, are provided in order to convey refrigerant in the defrost circuit 54, in a selected sequence. For instance, refrigerant in the defrost circuit 54 may be sent directly to the heat-reclaim coils 56 so as to heat ventilation ducts or a water reservoir. Alternatively, the refrigerant may be sent directly to the defrost accumulator 55 after having absorbed heat from the first refrigerant through the heat exchanger 50. Finally, and as will be described hereinafter, the refrigerant may be sent to the feed header 58 so as to return through the return header 59 in a defrost of the evaporators of the refrigeration cabinets.

The feed header 58 taps into the feed line 84, and has valves that are controlled to open the feed header 58 to the feed line 84, and hence to the evaporators 86. Similarly, the return header 59 is connected to the lines 88, and has valves that are controlled to open the return header 59 for the line 88.

Defrost Operating Sequence

As the refrigerant that will be used for the defrost cycle of the evaporators 86 will be using the same lines as the evaporator circuit 19, it is preferred to provide the defrost circuit 54 with the second refrigerant (e.g., glycol/water mixture), like the evaporator circuit 19, so as to avoid potential contamination.

In order to lessen energy loss, the refrigeration system 10 operates a flushing sequence by which the second refrigerant in heat-absorbing refrigerating condition, as is present in the lines 84, 88 and the evaporators 86, is flushed out therefrom prior to the second refrigerant in heat-releasing defrosting condition being fed to the evaporators 86 and lines 88, thereby avoiding the mixture of the second refrigerant in these two conditions. In order to do so, valve D1 (normally closed) on the pressure line 91 will be opened, while valve D2 (normally closed) is kept closed, so as to supply the feed header 92 with pressure from the pressure source 90. Selected evaporators 86 will remain open such that the pressure will flush the refrigerant out of these selected evaporators 86, while others that do not require defrost will be closed to avoid the flush pressure. Although unidentified in FIG. 1, controllable valves (e.g., solenoid valves) are appropriately provided upstream and downstream of each of the evaporators 86 to enable the selection of some evaporators 86 for defrost.

Therefore, the flush pressure will cause the flush of the evaporators 86 of the second refrigerant in the heat-absorbing refrigerating condition. The second refrigerant in the heat-absorbing refrigerating condition will leave the selected evaporators 86 to return to either one of the transfer accumulators 80 and 80′, depending on the sequence which the evaporator circuit 19 is at. Once the selected evaporators 86 have been flushed out of the second refrigerant in the heat-absorbing refrigerating condition, valve D1 is closed such that the second refrigerant in the defrost circuit 54 (i.e.., in the heat-releasing defrosting condition) may reach the selected evaporators 86 through the feed header 58. The return header 59 defines a path by which the defrost second refrigerant will return from the selected evaporators 86 to the defrost accumulator 55. The unidentified valves of FIG. 1 that enable the feed of refrigerant to the evaporators 86 are controlled to stop the feed of the second refrigerant in the heat-absorbing refrigerating condition to the selected evaporators 86, and enable the feed of the second refrigerant in the heat-absorbing refrigerating condition from the feed header 58 to the selected evaporators 86. The refrigeration system 10 therefore enables the simultaneous defrost and refrigeration cycles to operate in the evaporation stage, with some of the evaporators 86 being used to cool air, while others are being defrosted.

Once the selected evaporators 86 have been defrosted, a flush of the selected evaporators 86 is performed so as to remove the hot second refrigerant from the selected evaporators 86 for the subsequent feed of cool second refrigerant (from the evaporator circuit 19) to the selected evaporators 86. Accordingly, the flush prevents the mixture of the cool second refrigerant of the evaporator circuit 19 with the hot second refrigerant of the defrost circuit 54. To perform the flush of the defrost second refrigerant, valve D2 is opened while valve D1 is kept closed, and only the selected evaporators 86 are opened for fluid communication with the headers 58, 59. Accordingly, pressure from the pressure source 90 will build in feed header 58, so as to flush the hot second refrigerant from the selected evaporators 86, such that the hot second refrigerant exits through the return header 59 and gathers thereafter in the defrost accumulator 55 or other apparatus of the defrost circuit 54.

Energy Accumulator Circuit Portion

Referring to FIG. 1, the evaporator circuit 19 optionally has an energy accumulator circuit portion. The energy accumulator circuit portion has an energy accumulator 94 that is in fluid communication with the transfer accumulator 80 through lines 95. Valves E1 and E2 are provided in lines 95. Moreover, the energy accumulator 94 is connected to the pressure lines 91 and separated therefrom by valve F1. In the embodiment of FIG. 1, pressure differential is used to transfer refrigerant between the energy accumulator 94 and the transfer accumulators 80 and 80′, with appropriate valve operating sequences for valves E1, E2 and F1. Alternatively, pumps may be provided on the lines 95 so as to convey refrigerant from the transfer accumulator 80 to the energy accumulator 94.

For instance, the energy accumulator circuit portion operates at night when the demand for refrigerant from the evaporators 86 is low (e.g., cooler outdoor temperature, refrigerated cabinets are not opened up, stores are closed, etc.), but when tariffs are also low, so as to store a greater amount of energy than would be possible with the transfer accumulators 80 and 80′. The transfer accumulator 80 cools the second refrigerant, which is sent for storage to the energy accumulator 94. Moreover, warm refrigerant from the energy accumulator 94 may be sent to the transfer accumulator so as to be cooled.

Thereafter, the pressure source 90 is used in order to convey the second refrigerant from the energy accumulator 94 to the transfer accumulator 80, when there is demand from the evaporators 86. Accordingly, valves E1 and E2 are operated to enable circulation of refrigerant between the transfer accumulator 80 and the energy accumulator 94.

Alternative Embodiments

Referring to FIG. 2, a refrigeration system in accordance with an alternative embodiment of the present invention is generally shown at 10′. The refrigeration system 10′ of FIG. 2 is similar to the refrigeration system 10 of FIG. 1, whereby like elements will bear like reference numerals. Elements of the refrigeration system 10 that are different from that of the refrigeration system 10′ will have reference numerals between 100 and 199, inclusively.

The refrigeration system 10′ has an evaporation circuit 119 that differs from the evaporator circuit 19 of FIG. 1, in that the second refrigerant in the evaporation circuit 119 is pumped to the evaporators 86, rather than being entrained by pressure differential. More specifically, line 84, which interrelates the transfer accumulators 80 and 80′ to the evaporators 86 (only one of which is shown in FIG. 2), is provided with a pump 100, which induces the flow of the second refrigerant from the transfer accumulators 80 and 80′ to the evaporators 86, and back to the transfer accumulators 80 and 80′. The above-described sequence of having one of the transfer accumulators 80 and 80′ feeding the evaporators 86, while the other of the transfer accumulators 80 and 80′ is in heat-exchange with the main circuit 11 for cooling the second refrigerant, is followed. Therefore, a set of valves, not shown in FIG. 2, is controlled to ensure the sequence is followed.

The refrigeration system 10′ has a pressure source 190, which differs from the pressure source 90 of FIG. 1, in that it is used for the flushing operations when defrost of some of the evaporators 86 is required, as described above for the refrigeration system 10. Therefore, the line 91 connects the pressure source 190 to the line 84, to flush the second refrigerant in the heat-absorbing refrigerating condition back into the transfer accumulators 80 and 80′, and to the line 57, to flush the second refrigerant in the heat-releasing defrosting condition back into the defrost accumulator 55. The valves D1 and D2 are controlled to cause the above-described flushes.

The energy accumulator 94 is connected to both transfer accumulators 80 and 80′ by line 195. A pump 102 is provided on the line 195 to induce circulation of the second refrigerant between the transfer accumulators 80 and 80′, and the energy accumulator 94.

The use of pumps in the refrigeration system 10′, as opposed to compressed air in the refrigeration system 10 (FIG. 1), is advantageous in that the transfer accumulators 80 and 80′, and the energy accumulator 94 need not be adapted to maintain the second refrigerant pressurized. Because of the volume of the transfer accumulators 80 and 80′, and the energy accumulator 94, and the relatively high pressure (i.e., above atmospheric pressure) necessary to induce the circulation of the second refrigerant in the refrigeration system 10 of FIG. 1, the various accumulators 80, 80′ and 94 must have the structural integrity to operate under such conditions, whereby the use of pumps represents a cost-efficient alternative.

Referring to FIG. 3, a refrigeration system in accordance with another embodiment of the present invention is generally at 10″. The refrigeration system 10″ of FIG. 3 is similar to the refrigeration system 10 of FIG. 1, and the refrigeration system 10′ of FIG. 2, whereby like elements will bear like reference numerals.

The refrigeration system 10″ has an evaporation circuit 219, essentially similar to the evaporator circuit 19 of the refrigeration system 10 of FIG. 1, but without an energy accumulator. Therefore, the refrigeration system 10″ does not have an additional reservoir to accumulate energy, for instance when fuel/electricity tariffs are low. Energy may be stored in the transfer accumulators 80 and 80′.

In FIGS. 2 and 3, the refrigeration systems 10′ and 10″, respectively, have compressors 120′ that differ form the compressors 20 of the refrigeration system 10 of FIG. 1. More specifically, the compressors 120′ are compressors that can operate at lower minimum compression ratios than typical compressors. For instance, Turbocor (www.turbocor.com) has designed an oil-free magnetic-bearing compressor that can safely operate at the aforementioned compression ratios.

At such low compression ratios, typical compressors have been subjected to failure. For this reason, the refrigerant has been over-compressed to a minimum operating pressure in view of the subsequent condensing stages, when the outdoor temperatures are low. The Turbocor compressor may thus compress the first refrigerant to pressures better suited for cold outdoor temperatures (i.e., lower pressures), thereby causing reductions in energy consumption, as previous compressors typically have a minimum operating pressure at which they operate for cold outdoor temperatures. However, the expansion valves of the expansion stage 16 require minimum refrigerant pressures to operate, whereby it is contemplated to provide pumps 104 to increase the refrigerant pressure upstream of the expansion stage 16, to ensure the first refrigerant is in an appropriate condition for expansion. Electronic/automatic expansion valves could be used as an alternative to the pumps 104, as pressure increasing means.

Transfer Accumulators

Referring to the drawings and, more particularly, to FIG. 4, a transfer accumulator, such as the transfer accumulators 80 and 80′, is generally shown at 300. The transfer accumulator 300 is shown having a wall thereof removed to illustrate its interior.

The transfer accumulator 300 has a vessel body 302 that accumulates the second refrigerant of the evaporator circuit 19 (FIGS. 1-3), which circulates through the vessel body 302 by the inlets 303 and outlets 305. A heat exchanger 304 passes through the vessel body 302, and is immersed in the second refrigerant accumulated in the vessel body 302. The first refrigerant of the main circuit 11 (FIGS. 1-3) circulates through the heat exchanger 304 so as to be in a heat-exchange relation with the second refrigerant in the vessel body 302, as described above for FIGS. 1-3. The heat exchanger 304 is a plate heat exchanger, having a plurality of plates 306 through which the first refrigerant circulates, through inlets 308 and outlets 310.

Accordingly, the second refrigerant accumulating in the vessel body 302 is preferably subjected to a phase change, according to its nature. For instance, a glycol/water mixture used as second refrigerant typically becomes slushy at the heat-exchange conditions in the vessel body 302. Therefore, as illustrated in FIG. 4, moving knives 312 are mounted onto the plates 306, and are displaceable along direction A so as to break any solid build-up on the plates 306. The displacement of the moving knives 312 may be actuated using compressed air from the pressure source 90 (FIGS. 1 and 3), or the pressure source 190 (FIG. 2). The moving knives 312 may alternatively be motorized.

In FIG. 5, there is shown an alternative configuration for the heat exchanger 304, in that the plates 306 of FIG. 4 are substituted by coils 314. Therefore, the moving knives 312 are equipped to break solid build-ups between the passes of the coils 314.

In the event that the transfer accumulator 300 is used in the refrigeration systems of FIGS. 1 and 3, the vessel body 302, must be a pressure chamber, capable of sustaining the pressure supplied by the pressure source 90. In such as case, a bleed valve 316 is provided to ensure the pressure within the vessel body 302 remains below expected levels.

In the embodiments of FIGS. 1 to 3, there are a pair of transfer accumulators according to the sequence of steps through which the second refrigerant goes. In order to provide feedback to a controller to ensure the proper operation of the evaporator circuit 19, level detectors (e.g., optical, mechanical) are typically provided in the vessel body 302 to signal when it is required to shift the feeding sequence from one accumulator to another.

It is contemplated to provide alternative solutions to embody the heat-exchange relation between the first and the second refrigerant. For instance, a slush-making machine, having a rotary knife that prevents solid build-ups on the heat exchangers, may be used in accordance with the embodiments of the present invention.

It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims. 

1. An evaporator circuit for a second refrigerant used in conjunction with a refrigeration circuit of the type operating a refrigeration cycle having a compression stage, a condensation stage, an expansion stage, and an evaporation stage with a first refrigerant, comprising: a heat exchange stage having at least one heat exchanger in a refrigerant accumulator in which the second refrigerant is in heat-exchange relation with the first refrigerant circulating in the heat exchanger in the evaporation stage of the refrigeration circuit, the heat exchanger being positioned in the refrigerant accumulator so as to be immersed in the second refrigerant such that the second-refrigerant releases heat to the first refrigerant circulating in the heat exchanger; and an evaporator stage having at least one evaporator in which the second refrigerant absorbs heat from a fluid passing through the evaporator, so as to cool the fluid; whereby the second refrigerant circulates between the heat exchange stage and the evaporator stage.
 2. The evaporation circuit according to claim 1, wherein the heat exchange stage has two of the heat exchanger each in a respective refrigerant accumulator, such that the second refrigerant in the refrigerant accumulators is sequentially (1) in heat-exchange relation with the first refrigerant while receiving the second refrigerant from the evaporator stage, and then (2) fed to the evaporator stage, with the first and the second refrigerant accumulators alternating sequentially with respect to one another.
 3. The evaporation circuit according to claim 1, further comprising an energy accumulator in fluid communication with the heat exchange stage, such that the second refrigerant having released heat to the first refrigerant may be stored in the energy accumulator, for subsequently being used in the evaporator stage.
 4. The evaporator circuit according to claim 1, wherein at least one pump is used to induce fluid circulation between the heat exchange stage and the evaporator stage.
 5. The evaporator circuit according to claim 1, wherein a pressure source pressurizes the refrigerant accumulator to induce fluid circulation between the heat exchange stage and the evaporator stage.
 6. The evaporator circuit according to claim 1, wherein the second refrigerant changes phase from liquid to solid in the heat-exchange relation with the first refrigerant, a tool being provided on the heat exchanger so as to remove solid build-up of the second refrigerant on the heat exchanger.
 7. A refrigeration system of the type having a refrigeration circuit having a compression stage, a condensation stage, an expansion stage and an evaporation stage through which a first refrigerant circulates, further comprising an evaporator circuit through which circulates a second refrigerant between a heat exchange stage having at least one heat exchanger in a refrigerant accumulator in which the second refrigerant is in heat-exchange relation with the first refrigerant circulating in the heat exchanger in the evaporation stage of the refrigeration circuit, the heat exchanger being positioned in the refrigerant accumulator so as to be immersed in the second refrigerant such that the second refrigerant releases heat to the first refrigerant circulating in the heat exchanger, and an evaporator stage having at least one evaporator in which the second refrigerant absorbs heat from a fluid passing through the evaporator, so as to cool the fluid for refrigeration, whereby the second refrigerant circulates between the heat exchange stage and the evaporator stage.
 8. The refrigeration system according to claim 7, further comprising a defrost circuit in which the second refrigerant circulates, and being in a heat exchange relation with the first refrigerant at the condensation stage of the refrigeration circuit so as to absorb heat from the first refrigerant, the defrost circuit being in a controlled fluid communication with the evaporator of the evaporator stage of the evaporation circuit, so as to defrost the at least one evaporator with the second refrigerant that has absorbed heat in the heat exchange relation with the first refrigerant.
 9. The refrigeration system according to claim 7, wherein the heat exchange stage has two of the heat exchanger each in a respective refrigerant accumulator, such that the second refrigerant in the refrigerant accumulators is sequentially (1) in heat-exchange relation with the first refrigerant while receiving the second refrigerant from the evaporator stage, and then (2) fed to the evaporator stage, with the first and the second refrigerant accumulators alternating sequentially with respect to one another.
 10. The refrigeration system according to claim 7, further comprising an energy accumulator in fluid communication with the heat exchange stage, such that the second refrigerant having released heat to the first refrigerant may be stored in the energy accumulator, for subsequently being used in the evaporator stage.
 11. The refrigeration system according to claim 7, wherein at least one pump is used to induce fluid circulation between the heat exchange stage and the evaporator stage.
 12. The refrigeration system according to claim 7, wherein the second refrigerant changes phase from liquid to solid in the heat-exchange relation with the first refrigerant, a tool being provided on the heat exchanger so as to remove solid build-up of the second refrigerant on the heat exchanger.
 13. The refrigeration system according to claim 8, wherein a pressure source is connected to the at least one evaporator of the evaporator stage to flush the first refrigerant out from the at least one evaporator for subsequent defrost of the evaporator, and after the defrost of the evaporator.
 14. The refrigeration system according to claim 13, wherein the pressure source is connected to the refrigerant accumulator so as to pressurize the refrigerant accumulator to induce fluid circulation between the heat exchange stage and the evaporator stage.
 15. A refrigeration system of the type having a refrigeration circuit having a compression stage, a condensation stage, an expansion stage and an evaporation stage through which a first refrigerant circulates, comprising: at least one compressor at the compression stage, the compressor being a magnetic-bearing compressor; and pressure increasing means upstream of the expansion stage, so as to increase the pressure of the first refrigerant for subsequently being fed to the expansion stage. 